1. Field of the Invention
The present invention relates to an atmospheric gas burner assembly comprising a burner tube defining a multiplicity of gas outlet ports producing flames in a flame area above the tube and an element reducing the flame temperature and, hence, emission of oxides of nitrogen disposed above the burner tube in the flame area.
2. Description of the Prior Art
Concerning the so-called NO.sub.x emission of heating systems operated by oil or gas burners, reference is made to "Gas-International", vol. 30 (1981), No. 1, pp. 41 and 42. General pollution problems have raised the question of NO.sub.x emission in heating systems, with efforts being made to reduce the NO.sub.x emission as far as possible. It has been suggested to protect the burner tubes, at the flame side thereof, by a fine mesh metal screen to thereby cool the flame and radiate away the heat absorbed by the element reducing the NO.sub.x formation. In respect of oil burners, the afore-mentioned article, among other things, contemplates a reducing element for this purpose, which is of a semi-spherical, perforated bowl configuration. It has been found especially with atmospheric gas burners that such inserts or flame baffles are capable of preventing the oxygen from the supplied secondary air from directly getting into contact with the peak flame temperature, thereby reducing the NO.sub.x formation. However, at the same time, it has been noted that in the event of an adverse influence of the element on the flame, the combustion reactions are affected thereby, causing enhanced CO formation; besides, this simple sort of protective baffles will not assure the maximum attainable NO.sub.x reduction which, presumably, is due to the fact that the flames are not adequately cooled. Presumably, this is also related to the geometry of the combustion chamber walls surrounding the burner tube, and to the geometry of the elements introduced into the peak flame areas and intended to reduce the NO.sub.x formation.